This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We are attempting to structurally characterize intermediates in the cell entry pathway of poliovirus, including soluble forms of the intermediates in vitro, membrane associated forms of the intermediates in vitro using a receptor-decorated liposome model, and intracellular forms of the intermediates in vivo. Although membrane fusion provides a conceptually simple pathway for genome delivery in enveloped viruses, nonenveloped viruses must provide a mechanism for transporting the genome or nucleoprotein complexes containing the genome across a membrane. This process is poorly understood. This specific experiment aims to characterize intermediates in various stages of releasing the genome, in hope of determining the site and mechanism of externalization.